Wooden floors are usually in the form of floorboards but can also be chipboard in more modern homes. Such floors are not the ideal surface to tile over for a number of reasons. They will flex when someone walks across them and also (especially in the case of floor boards) will expand and contract depending on the ambient temperature and humidity. But providing you are aware of the constraints of tiling over a wooden floor and prepare the substrate thoroughly, there is no reason why such a project cannot be done successfully and why it will not endure for many years to come without the tiles cracking or lifting. In fact, the preparation of a wooden floor for tiling is no more difficult than preparing any other substrate if you want to do a professional job.
The main point to remember is that you should never install tiles directly onto floorboards or chipboard (even the newer water-resistant chipboard).
First ensure you have the right equipment – the following items are always useful:
• Scoring Knife
• Flexible Tile Adhesive
• Flexible Tile Grout
• Tile Spacers
• Tile Cutter
• Small Saw
• Countersunk screws
So, first check for any loose boards and screw them into the joists – you should be able to gauge where the joists are because the existing nails or screws will usually run across the boards in a straight line corresponding to the location of the joists. Now you will need to lay a more robust layer over the wooden floor that will protect the tiles from the movement of the wooden substrate. The ideal surface for this is a 6mm tile backer board, which is a stable, waterproof board. Traditionally, 12mm marine plywood boards have been used for this purpose but tile backer board is now less expensive, and easier to cut and fit. But check out the costs of the different boards available in your area before making a decision. The method is the same for both types of board.
Tile backer board can be initially attached to the wooden floor with a good high-grab adhesive – always pressing down firmly to make sure the board has stuck to the floor, but should them be screwed into the floorboards with countersunk screws so that they are flush with the board. (Note, if you are using plywood then you should also screw into the joists.) Each tile backer board should be glued to the next one along the adjoining edge and this layer should be given added strength by layer the boards in a brick-type arrangement so the joints are staggered.
Tile backer boards can be easily cut to size by scoring and snapping in the same way that ceramic tiles can be cut. A small saw can be used to shape the board around pipes or other obstacles.
Once the floor is covered, apply a suitable primer and fix your tiles using a flexible adhesive and flexible grout for added protection against any movement of the substrate. If you have used a plywood base then you will need to fix the tiles with a 2 part adhesive – ask your tile supplier to recommend the best type of adhesive to use.